Technical Field
The present disclosure relates to a transformer, in particular to a padmount transformer, i.e. a ground mounted electric power distribution transformer housed in a locked cabinet to be mounted on a ground level platform or a concrete pad. The transformer according to the present disclosure is provided with an energy storage apparatus and is to be integrated in a system where at least some customers/loads supplied by the transformer are provided with renewable energy sources. The transformer according to the present disclosure is particularly suitable to handle the situation in which some customers/loads are subjected to black-outs and require technical solutions to manage the black-out conditions.
Description of the Related Art
Padmount transformers are used with underground electric power distribution lines at service drops and convert the power distribution network high or medium voltage to a low voltage supplied to loads, such as buildings, industries or the like. A single padmount transformer may serve one or more customers/loads.
Known padmount transformers include a transformer cabinet, usually housing a tank for holding the core/coil assembly of the transformer immersed in oil, and a wiring cabinet having compartments for enclosing the high/medium and low voltage bushings as well as medium voltage and low voltage connections and equipments.
Recently, the integration of renewable energy sources in electrical power systems are steadily increasing. In particular, it has become common to apply renewable energy sources, such as solar cells or wind generators, to the buildings which however maintains the connections with the power distribution network.
The renewable energy production tends to be variable and unpredictable. For example, considering the solar cells, there is an excess of power and energy generated during sunny hours of the day, which frequently do not correspond to the peaks of power demand by the loads. Under these circumstances, there is reverse flow of power in the power distribution network, (i.e. the renewable energy produced is supplied to the network), which should be reused when the production becomes lower than the load consumption. From an energetic point of view, this is not convenient because it causes power losses in the power distribution network since the energy has to be sent kilometres away to be used and the voltage at transformers side might increase and become too high to be acceptable for the electrical equipment forcing the electrical distributor in making important investments to manage the problem.
In order to deal with this issue, several solutions have been proposed.
A first proposed solution is that areas having a high concentration of renewable energy sources directly supply energy to areas having a lower concentration of/no renewable energy sources. This solution, however, is not fully satisfactory because it does not solve the problem of the shift between the peak of production and the peak of demand. Moreover, the energy produced by one are may be not sufficient for the area itself and the additional areas.
Another proposed solution is to provide the electric power distribution lines with energy storage systems. To this purpose, for example, it has been proposed to accumulate water through water pumping in some high altitude natural or artificial basins during the renewable energy peaks of production and then to withdraw the hydraulic energy during peaks of power demands. This solution however implies high investments in the network and does not solve the problem of power losses in the network since water basins can be extremely far away from the location where the energy is first produced.
Another proposed solution is to integrate each renewable power source with batteries able to accumulate small portions of produced energy. This solution however has the problem of a low effectiveness, leaves the problem to the discretion of the single user and is not satisfactory on a larger scale, for example in a city district where some users have renewable power sources with batteries and some other users have power sources with no batteries.
Finally, with reference to the problem of customers/loads particularly sensitives to black-outs, tailor-made solutions have been proposed, like installing an uninterruptable power supply (UPS) in every location needing a continuous flow of electrical energy supply even in presence of a black-out. However, this solution is expensive and requires a regular maintenance of UPS that a normal user might be not able to provide. Hence, there is desire and room for further improvements.